Johndp415

Hi guys,

I have a 2010 GS 450h with about 84,000 miles and over the last 6 months or so I noticed that my gas mileage has gone down and to me it feels like it's not as quick when you press the accelerator.

I used to average 21-22mpg on my 29 mile round trip commute over the bay bridge and back to San Francisco, but the last 6 months I have been averaging 17-19mpg and my driving style is the same and my route to work is the same.

I remember when being in both "Sport" and "Power" mode the car would literally feel like it is surging with power when you hit the gas pedal. Now, it still will accelerate quickly, but just feels less so than before. I'm going to try some Chevron fuel system cleaner at my next fill up to see if that helps my problem with power loss and mpg loss.

At my 80,000 mile service I did bring up the issue with Lexus of Serramonte and they performed a check on the hybrid system and said it seems ok to them. I told them I would keep an eye on it myself and will let them know if I keep having the same feeling of power loss and low mpg.

My question is how do I know if my hybrid battery is showing signs of it slowing dying or is about to need a replacement? Are there any signs that owners had that did replace their hybrid battery?

What i noticed:
*Less mpg
*Feels like it has less power
*The energy flow screen shows the battery charge to near full and then within 1/4-1/2 a mile of electric stop/go driving it's down to the purple bars, I remember being able to go further before getting the purple bars.

Thanks in advance for any advice

P.S. I tried to do a search for a similar question but didn't find one. I also posted in the hybrid section, just wondering if someone on the 3GS forum can help.

lexusisgs

if it is battery issue you will get code P0A80
display will say CHECK HYBRID BATTERY.
Now when that happend you can still drive car but no hybrid support.
usually when battery is bad you have to replace couple cells inside that battery ,depends which are bad.You can check one of my thread how to do it.
second gas milage sometimes is not related to the hybrid battery.It could be other things too.
Check your spark plugs
check your coils
check you MASS sensensor on air box( make sre it is clean)
check you air filter
check you brake calippers (just to make sure non of them have stuck pistons)
check for any vacuum leak
check if you muffler or cat isnt pluged
check you CVT transsmission fluid level after you change oil in it.

that what I will do .....good luck

lexusisgs

by the way have lexus deal to run diagnostic on your battery and see which block is reading low voltage.
In my gs 450h I have 20 blocks and each block has 2 battery cells in it ,measuring around 7.8v each.
Battery cells are easy to replace problem is to find some from junk yard .
Also camry and nissan and prius and lexus have same battery cells so it can be used.
I am using two cells from camry 2009 in my lexus.
​​​​​​​In nissan altima hybrid I have used cells from prius too.

703

Do a discharge cycle of the traction battery and use techstream to measure voltage difference between blocks. If it's more than 1.2v your battery is toast.